The reaction of an alkane in the presence of a catalyst to form unsaturated hydrocarbons is well known. If a chlorine source is present, chlorinated saturated and unsaturated hydrocarbons are also produced. Perhaps the most familiar of such processes is the preparation of vinyl chloride.
Vinyl chloride (CH.sub.2 .dbd.CHCl) itself can be prepared using a number of different processes. Two familiar processes are (1) the hydrochlorination of acetylene and (2) the oxychlorination of ethylene to form dichloroethane which in turn is dehydrohalogenated to form vinyl chloride (see C. A. Schildknecht, Vinyl and Related Polymers, John Wiley and Sons, Inc., N.Y., N.Y. (1952), pages 388-390, and U.S. Pat. No. 2,847,483). As acetylene is more expensive than ethylene, the latter process is economically favored, and much activity is noted in this art area (see U.S. Pat. Nos. 3,634,330; 3,454,663; 3,448,057; and 3,624,170). Ethylene, in turn, can be prepared by the oxydehydrogenation of ethane (see U.S. Pat. No. 3,769,362). The processes have been combined so that vinyl chloride can be directly produced using ethane as a feed stock (see U.S. Pat. Nos. 2,838,577; 3,658,933; 3,658,934, and 3,551,506). It is the nature of the processes which use ethane as a feed stock to produce vinyl chloride and ethylene, along with other valuable products such as ethylene dichloride and ethylene chloride. As ethylene, ethylene dichloride, and ethyl chloride can be readily reacted to form more vinyl chloride, the processes are often rated and compared on their ability to yield all four products. However, high conversion of ethane to products and high yield of vinyl chloride is particularly desired.
The present invention is directed to an improved process for the oxychlorination of an alkane and particularly for the preparation of ethylene and vinyl chloride from ethane which process employs specific solid solution catalysts containing iron. The catalysts of the invention exhibit improved activity and longer lifetimes compared to conventional iron containing catalysts. Catalysts containing iron are known to the art; see U.S. Pat. Nos. 3,849,339; 3,769,362; 3,723,351; 3,703,593; 3,658,934; 3,658,933; 3,207,809; 2,847,483; and 2,674,633, U.S. Publication No. B 380,979, and British Pat. No. 1,039,369. An article in the Journal of the American Ceramic Society, Vol. 43, No. 7 (1960), page 367, discloses compounds of lanthanum and iron and recently issued U.S. Pat. No. 3,904,553 discloses certain solid solutions as having activity as catalysts.